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Environmental Risk Assessment for Shale Gas Development
Daniel J. Soeder, NETL, Morgantown, WV
Presentation for Chesapeake Bay Program STAC
State College, PA, April 11, 2012
Concepts of Risk
Risk = probability x consequences
Risk in Engineered Geologic Systems
Threat: external events that cause risk
Threats can exploit vulnerabilities
Threats are assessed in terms of probability (Precautionary Principle)
Vulnerability: internal weakness that invites risk
Vulnerability only exists in the face of a threat
Vulnerability is assessed in terms of likely threats (Calculated Risk)
Both threats and vulnerabilities must be assessed to
properly understand risk.
Risk can vary over time >>
(CO2 injection example)
NETL Office of Research and Development
New program charge in 2011 for
EPAct projects: Assess risk from oil
and gas production
Program Technical Areas:
primarily shale gas
Focus Areas for Risk Assessment:
Potential impacts from hydraulic
Potential impacts from poor
Potential impacts to water quality
Potential impacts to air quality
Potential Shale Gas Risks
Engineering Risk Assessment:
What is the probability of a contaminant release?
What is the probability of an induced seismic event?
What risks are short term versus long term?
What are the receptors?
Air, water, landscapes, ecosystems/habitat
The major unknown risk is cumulative effects
How will multiple wells make an impact?
What is threshold for impacts? (i.e. impervious surfaces)
Risk reduction through regulations and enforcement
Not all known environmental impacts are regulated
Not all regulations are fully enforced
Risk Assessment in Engineered Systems
DOE National Risk Assessment Partnership (NRAP) Cooperative effort among NETL, LBNL, LLNL, LANL, and PNNL
Scenario-based, site modeling for carbon storage in engineered
Sometimes called site performance assessment
Uses FEP-based scenarios and probabilities Feature: property of a geologic system that may affect risk
Event: an action that introduces higher risk conditions into a system
Process: a method or procedure that increases risk
Predict performance of components using high fidelity
Run scenarios to validate models/reduce uncertainty
Provide quantitative basis for geologic storage security
Integrated Risk Assessment Models
Integrated Assessment Models (IAM) Probabalistic assessment of system risk (multi-site)
Interaction of sites can increase or decrease risk
Divide system into components, develop detailed,
validated models, reduce uncertainty
Develop reduced order models (ROM) to reproduce
detailed model predictions of components
Integrate ROMs through IAM to predict total system
performance, interactions and risk
Calibrate using field data and databases
Quantify potential long-term liability
Risk Profile Risk Management Validation
(Quantify) (Strategy) (Field Data)
Adapting NRAP to Shale Gas
Components: old wells with
potential casing and cement
integrity issues, watered-out
Design Basis: greatest risk
is immediately after injection;
when pressure is highest.
Model: seal integrity, well
bore leakage, migration
through intermediate strata,
changes in pressure and
verification and accounting
Components: new wells,
with new fractures, tight, dry,
Design Basis: greatest risk
is after frac during early
stages of production under
initial high pressure.
Model: fracture heights,
fresh groundwater depth,
bypass flowpaths, wellbore
Validation: field monitoring
and analyses (need defining)
Risk Assessment via Incident Reports One method to help determine the components of an IAM is to
review past incident data at oil and gas production sites.
Reporting only the number of incidents is meaningless: Discharge of industrial waste can range from a spilled quart of motor oil to a leak from a ten thousand
gallon frac fluid tank.
Classification of incidents:
Administrative: missing signage, poor record-keeping, incorrect permit application or
other missing or wrong "paperwork."
Minor: small spills or leaks that require clean up, but are contained on site, do not
enter the groundwater, and can be remediated by the local rig crew.
Significant: larger spills or leaks that could potentially leave the site but did not, and
required outside assistance (i.e. HAZMAT team) to help clean up.
Serious: explosion, fire, stream contamination or fish kill, human injury or fatality,
significant property damage, contamination of a drinking water supply.
Catastrophic: destruction of site and serious damage to surrounding area.
Frequency, type and seriousness of incidents over time help define
State regulatory agencies are the source of most incident reports.
Water Contamination Incidents Kell, Scott, 2011, State Oil and Gas Agency Groundwater
Investigations and their Role in Advancing Regulatory Reforms: A Two-
State Review: Ohio and Texas, Groundwater Protection Council, 165
p., August 2011, Oklahoma City, OK:
Incident: "any detected contamination of groundwater or disrupted water
supply due to development of oil and gas or management of wastes."
Ohio reported 144 incidents in 33,304 wells between 1983 and 2007
(rate = 0.432%); no significant shale gas production at the time.
Most Ohio incidents occurred during drilling/production operations
85 of the 144 incidents (60%) occurred between 1983 and 1988 (boom).
Texas reported 211 incidents in 187,788 wells between 1993 and
2008 (rate = 0.112%); Barnett Shale play began in 1997.
Most Texas incidents occurred during waste disposal
Texas RR Commission "witnesses" drilling and completion operations on
about 1/3 of wellsites
Both states reported zero incidents over the time periods studied
associated with well stimulation (hydraulic fracturing)
Water Resource Risks/Questions Supply
3 to 4 million gallons per well
2/3 to 3/4 consumptive use
Watershed management vs. stress
Watershed Impacts Stream degradation from roads-pads-operations
Water quality degradation from leaks/spills
Groundwater Infiltration from above
Frac fluid/formation water from below
Changes in GW flow directions or gradients
Fate of fluids that remain underground
Water quality Infiltration of chemicals/spills into shallow
Long-term leaching of drill cuttings
Minerals-sediment-gas contaminating nearby water wells
Hydraulic Fracture Heights and Aquifers
1 51 101 151 201 251 301 351
Frac stages (sorted on Perf Midpoint)
Marcellus Mapped Frac Treatments
fracBTM Microseismic data, plotted against deepest freshwater aquifer on a county by county basis.
Reference: Fisher, Kevin, 2010, Data confirm safety of well fracturing, The American Oil and Gas Reporter, July 2010, www.aogr.com
Surface Leaks and Spills
Higher risk to groundwater and surface
water than frac fluid underground (Groat,
UT Austin study, 2012)
Baseline data on existing contaminants are
required to assess drilling impacts.
Studies underway in 2012:
Retrospective investigation of impacted
streams; large and small watersheds
Comparison of stream reaches: affected
and unaffected; also compare two similar
small watersheds (WVU)
Comparison of impacts versus watershed
management practices (Pitt)
Assessment of impacts, damage, costs
Forensics of what caused the leak
Better leak detection and warning, including
field-deployable instruments to monitor
surrogates (pH, conductance, turbidity)
Prospective data from Marcellus Test Site
Photo by Doug Mazer, used with permission.
Geochemistry of Shale Drill Cuttings Vertical: 5 metric tons of cuttings
Horizontal: 270 metric tons of cuttings
Anoxic black shales preserved organic
material with associated radionuclides.
Highest gas content is in the organic-rich,
radioactive black shale; cuttings at surface
are exposed to air and rainwater
Oxidized forms of these metals are much
more soluble and mobile
TimeofFlight Secondary Ion Mass Spectrometry (TOFSIMS) to determi